Rotary well tools and other driven rotary mechanisms often comprise relatively rotating components which are sealingly engaged with one another at a radial interface between the components. Some rotary assemblies, for example, comprise a driven shaft received in a non-rotating housing assembly (such as, for example, a co-axial tubular housing or sleeve forming part of a drill string), allowing rotation of the driveshaft relative to the housing assembly to which it is secured. In some rotary assemblies, however, a rotatable sleeve or housing seemingly receives a co-axial non-rotating shaft or mandrel.
Examples of sealed rotary assemblies include rotary steering tools connected in-line in the drill string and providing a housing sleeve that non-rotatably engages a borehole wall for steering purposes, while allowing sealed rotation of a tubular driveshaft passing therethrough. To protect the driveshaft from wear at the rotary seal interface, a removable and replaceable wear sleeve is often mounted on the driveshaft, being radially sandwiched between the rotary seal and the driveshaft. A radially outer wear surface of the wear sleeve is thus exposed to rotating sealing contact with the rotary seal.
Relative movement between the wear sleeve and the shaft is undesirable. Relative rotational movement can be caused by friction exerted by the rotary seal on the sleeve. Such rotational movement of the sleeve on the shaft would inevitably lead to failure of seals between the shaft and the sleeve, which are designed for static sealing.
Radial movement of the sleeve on the shaft can cause eccentric forces to be placed on the rotary seal, which would detrimentally affect seal life. Axial movement of the sleeve can lead to fretting issues of not only the primary rotary seal, but also of seals between the wear sleeve and the shaft.